In an ophthalmic apparatus designed to obtain information unique to an eye to be examined by projecting a light beam onto the eye and receiving the reflected light, a fixation mark for stabilizing a vision fixation state by fixing the eye is provided.
There has recently been known an ophthalmic apparatus which includes a detection means for detecting a light beam projected onto the cornea or the like of an eye to be examined, and a driving means for moving an eye examination unit in the up and down direction, the left and right direction, and the back and forth direction, or any thereof, and aligns the eye with an apparatus optical system by controlling the driving means on the basis of the detected eye position.
In such an ophthalmic apparatus, an examiner roughly aligns an eye to be examined with an eye examination unit by operating an operation means such as a console or a trackball so as to depict an image of the eye on a monitor to some extent, and presses a measurement switch upon completion of the alignment. When the measurement switch is pressed, the relative position between the eye and the eye examination unit is detected, and the driving means is controlled to make the eye examination unit coincide with the position of the eye. When the misalignment between the eye and the eye examination unit reaches a value within a predetermined allowable amount, ophthalmic examination such as measurement or photography is started.
The ophthalmic apparatus disclosed in Japanese Patent Laid-Open No. 10-14878 includes a vision fixation state determination means for determining the quality of the vision fixation state of an eye to be examined on the basis of detection results obtained by a pupil detection means and an alignment index projection/detection optical system. This apparatus detects the vision fixation state of the eye and starts measurement when determining that the vision fixation state of the eye is proper.
The fundus photographing apparatus disclosed in Japanese Patent Laid-Open No. 10-118030 has a plurality of fixation marks having different sizes which are presented to eyes to be examined, and can present a subject to be examined who has a visual disorder such as cataract or amblyopia with a large fixation mark which is easy to visually recognize.
According to the ophthalmic apparatus in Japanese Patent Laid-Open No. 10-14878, if a subject to be examined is, for example, a person who has a visual disorder such as cataract or amblyopia or an infant, it is difficult to make the subject determine where the fixation mark is located. In examining such a subject, therefore, the vision fixation state determination means for determining the quality of the vision fixation state of an eye to be examined determines a fixation failure on the basis of detection results obtained by the pupil detection means and the alignment index projection/detection optical system. In this case, a measurement permission is not issued, and the examination time prolongs. As a result, the vision fixation state of the eye becomes more unstable, and the measurement lasts forever.
The fundus photographing apparatus in Japanese Patent Laid-Open No. 10-118030 presents a subject to be examined who has a visual disorder such as cataract or amblyopia with a large fixation mark which is easy to visually recognize. Assume that the initial position of the optical axis direction of a fixation mark presented by the ophthalmic apparatus greatly differs from the line of sight of an eye to be examined. In this case, even if a large fixation mark is presented to the eye, the subject cannot recognize where the fixation mark is located, and it may be difficult to stabilize the line of sight.
If, therefore, a person who has poor eyesight, an infant, or the like is a subject to be examined, such a conventional ophthalmic apparatus cannot make the subject recognize where a fixation mark is located, and hence it is difficult to stabilize a vision fixation state. As a consequence, the accuracy of automatic alignment deteriorates, and the reliability of examination deteriorates. In addition, the examination time prolongs. In some cases, alignment cannot be completed, and examination cannot be performed.